As an electronic device, for example, an electronic device referred to as an MCM (Multi Chip Module) is known. The MCM mounts a plurality of semiconductor chips each incorporating an integrated circuit therein on a printed wiring board on which a wiring pattern is formed and constitutes one compact function. In this MCM, to increase the data transfer speed and to achieve the miniaturization of the electronic device, the trend to adopt a flip-chip packaging technique has become active. The flip-chip packaging technique is a technique which mounts semiconductor chips each arranging projection electrodes on one main surfaces thereof on a printed wiring board.
With respect to the flip-chip packaging technique, various mounting methods have been proposed and put into practice. As typical mounting methods among these mounting methods, for example, a method which is referred to as CCB (Controlled Collapse Bonding) and a method which is referred to as ACF (Anisotropic Conductive Film) mounting have been put into practice.
The CCB mounting method is a method which uses semiconductor chips having solder bumps made of a metal material of lead(Pb)-tin(Sn) composition, for example, as projection electrodes on one main surface, wherein the semiconductor chips are mounted on the printed wiring board by melting the solder bumps. This CCB mounting method is, for example, described in “electronic material” [1996, April issue, pp.14–19] “published by Kogyo Chosakai”.
As electronic components which are mounted on the printed wiring board by melting the solder bumps as in the case of the CCB mounting method, besides semiconductor chips (semiconductor chips for connecting solder bumps), there have been known semiconductor devices of a BGA (Ball Grid Array) type which packages semiconductor chips, a CSP (Chip Size Package or Chip Scale Package) type and the like. This type of semiconductor device mounts semiconductor chips on one main surface side of a printed wiring board which is referred to as an interposer and arranges semiconductor bumps as projection electrodes on another main surface (rear face) side which faces one main surface of the printed wiring board.
Further, in the CSP type semiconductor device, a CSP type semiconductor device having a new package structure which is manufactured by a manufacturing technique which integrates a wafer process (preceding step) and a package process (succeeding step) (wafer level CSP type semiconductor device) has been commercialized. In this wafer level CSP type semiconductor device, a planer size of the package is substantially equal to a planer size of the semiconductor chip and hence, it is possible to realize the miniaturization and the reduction of cost compared to the CSP type semiconductor device (chip level CSP type semiconductor device) which is manufactured by applying the packaging process to each semiconductor chip divided from a semiconductor wafer.
The wafer-level CSP type semiconductor device substantially includes a semiconductor chip layer, a rewiring layer (pad rearranging layer) which is formed over one main surface of the semiconductor chip layer and solder bumps which are arranged on the rewiring layer as projection electrodes. The semiconductor chip layer is substantially constituted of a semiconductor substrate, a multilayered wiring layer which is formed by stacking insulation layers and wiring layers respectively in a plural stages on one main surface of the semiconductor substrate and a surface protective film which is formed such that the surface protective film covers the multilayered wiring layer. Electrode pads are formed over an uppermost wiring layer out of the multilayered wiring layer and bonding openings which expose the electrode pads are formed in the surface protective film. The rewiring layer is a layer which is served for forming electrode pads having a wider arrangement pitch with respect to the electrode pads of the semiconductor chip layer. The electrode pads of the rewiring layer are electrically connected with the corresponding electrode pads of the semiconductor chip layer and are arranged at the same arrangement pitch with connecting portions which are arranged on a region of the printed wiring board on which the wafer level CSP type semiconductor devices are mounted. The solder bumps are arranged on the electrode pads of the rewiring layer and are electrically and mechanically connected with the electrode pads of the rewiring layer. The wafer level CSP type semiconductor devices are described in “Nikkei Micro Device” [1998, August issue, pp44–71] published by Nikkei Bp Ltd., for example.
Here, in this specification, the wafer level CSP type semiconductor device is also defined as a type of semiconductor chip.
The ACF mounting method is a method which uses semiconductor chips having stud bumps made of gold (Au), for example, as projection electrodes on one main surface and mounts the semiconductor chips on a printed wiring board by compression-bonding the semiconductor chips while heating the semiconductor chips in a state that an anisotropic conductive resin film (ACF) is interposed between the printed wiring board and the semiconductor chips as an adhesive resin. The anisotropic conductive resin film is a sheet which is produced by forming an insulation resin in which a large number of conductive particles are dispersed therein into a sheet shape, wherein an epoxy-based thermosetting type resin, for example, is used as the insulation resin. The stud bumps made of Au constitute balls by melting distal ends of Au wires and, thereafter, the balls are compression-bonded under heat to electrode pads which are arranged on one main surface of the semiconductor chip while applying ultrasonic vibration and, thereafter, ball portions are cut out from the Au wire thus forming the semiconductor chip. The ACF mounting method is, for example, described in Japanese unexamined patent publication 345041/1992 and Japanese unexamined patent publication 175280/1993.
As a mounting method which mounts semiconductor chips (stud-bump connection semiconductor chips) using thermo compression bonding as in the case of ACF mounting method, besides the ACF mounting method, there exists an NCF mounting method which uses an insulation resin film in which conductive particles are not mixed (NCF: non-conductive film) as an adhesive resin, an ACP mounting method which uses a paste-like anisotropic conductive resin (ACP: anisotropic conductive paste) and the like.